Add ClusterClass proposal API types

[fabriziopandini]

Detailed Description

As an initial activity for the implementation of the ClusterClass proposal we should add/change API types ad defined in the proposal.

This change should also include web hook changes as defined by the document in the validation paragraph; This can be eventually a follow up PR if we want to parallelise work.

With this regard I suggest some small amendments to the proposal

ClusterClass

• For object updates:
  • spec.worker.deployments[i].class field must be unique within a ClusterClass (added; it is already there for object create)

Cluster

• For object creation:

  • spec.topology and spec.infrastructureRef cannot be simultaneously set (added; there is already a similar check for controlPlaneRef)

@srm09 @vincepri PTAL to the proposed amendments to the proposal

/kind feature

[fabriziopandini]

/assign

[srm09]

Nice catch @fabriziopandini , missed these :)